just
The Italian word 'giusto' is used in the same sense as 'just' in English, both when 'just' means 'recently' (Ho giusto finito di lavorare meaning 'I just finished working') and when 'just' is used to emphasize that something is exact (Tre euro è il prezzo giusto meaning 'Three euros is just the right price').
The calculation you made is correct.
In this instance, 'giusto' is used to indicate correctness or rightness. It implies that the calculation made was accurate and is therefore 'correct'.
You are on the right road.
In this context, 'giusto' means 'right' as in 'correct'. It conveys the message that the person being addressed is on the appropriate or correct path.
You have just the time for a coffee.
Here, 'giusto' is used to indicate an exact or precise amount. In this case, it implies that there is just the right amount of time to have a coffee and nothing more.